PT - JOURNAL ARTICLE AU - G. Lefebvre AU - M. Lebreton AU - F. Meyniel AU - S. Bourgeois-Gironde AU - S. Palminteri TI - Optimistic reinforcement learning: computational and neural bases AID - 10.1101/038778 DP - 2016 Jan 01 TA - bioRxiv PG - 038778 4099 - http://biorxiv.org/content/early/2016/10/03/038778.short 4100 - http://biorxiv.org/content/early/2016/10/03/038778.full AB - While forming and updating beliefs about future life outcomes, people tend to consider good news and to disregard bad news. This tendency is supposed to support the optimism bias. Whether this learning bias is specific to “high-level” abstract belief update or a particular expression of a more general “low-level” reinforcement learning process is unknown. Here we report evidence in favor of the second hypothesis. In a simple instrumental learning task, participants incorporated better-than-expected outcomes at a higher rate compared to worse-than-expected ones. In addition, functional imaging indicated that inter-individual difference in the expression of optimistic update corresponds to enhanced prediction error signaling in the reward circuitry. Our results constitute a new step in the understanding of the genesis of optimism bias at the neurocomputational level.